1. Field of the Invention
The present invention relates to image processing, in particular to methods and apparatus for registration and merging of a plurality of overlapping two-dimensional (2D) images of three-dimensional (3D) scenes, especially in cases where the 2D images are related to the 3D scenes by a projective (or camera) transformation. The invention also relates to apparatus for performing the disclosed image processing.
2. Description of the Related Art
In many fields of art and technology imaging of scenes that are too extended to be captured in a single camera image is important. Composite images of such scenes must be merged from individual overlapping images of more limited fields of view. One example of where image composition is useful is the formation of an image of an extended scene from the limited fields of view of a digital camera suitable for a PC. Another example is the formation of an image of an extended region of a patient from individual x-ray images which are usually of more limited fields of view.
In many cases, such as in the previous two examples, since individual 2D images are related to the 3D scene by projective transformations, pairs of the individual images to be merged are also related to each other by projective transformations. Consequently, as part of the image merging process, it is important to identify the best projective transformation relating each pair of overlapping 2D images so that by use of this transformation the images of the pair can be brought into registration.
Accordingly, methods have been developed and are known for determining such projective transformations. Typical of these methods is that disclosed in Schultz et al., 1999, IEEE International Conference on Acoustics, Speech and Signal Processing, vol. 4, pp. 3265–3268. Here, much attention is paid to automatically determining a plurality of pairs of corresponding points, one point of each pair being in each image, that is typically input in order to find the parameters of the projective transformation relating the images. Once the pairs of corresponding points in the two image are identified, actual determination of the projective transformation is disclosed to be routine.
However, merely routine determination of a projective transformation from a plurality of pairs of corresponding points has been discovered to often not be sufficiently stable or accurate. The relevant arts need a simple and accurate method of determining such projective transformations.
Citation of a reference herein, or throughout this specification, is not intended to be construed as an admission that such reference is prior art to the Applicant's invention of the invention subsequently claimed.